Caste Development and Its Seasonal Cycle in the Australian Harvester Termite, Drepanotermes Perniger (Froggatt) (Isoptera; Termitinae).

Abstract

The development of Drepanotermes perniger (Frogg.) in Australia is simple, with non-reproductive and reproductive lines separating at the first moult, a single worker line, a monomorphic soldier caste derived from two or three worker stages, and brachypterous neotenics formed by the premature metamorphosis of fifth-instar reproductive nymphs. Intercastes are known between soldier and fifth-instar reproductive nymph; presoldier and neotenic; and third-instar worker and fourth-instar reproductive nymph. All have substantially nymphal thoraces and abdomens, with minor intercaste modifications, and heads that are variously modified from nymphal towards soldier, presoldier or worker characteristics. The development of the castes shows a marked seasonal cycle, and only workers, soldiers and fourth-instar reproductive nymphs occur during the winter. Oviposition begins after the resumption of foraging in spring, and in the south growth and differentiation continue through much of the summer. Fourth-instar nymphs break diapause synchronously in early summer, and the alates fly with rains in January or February. In northern Australia there is a break in oviposition during summer, and the reproductive nymphs develop from eggs laid in autumn, after the alates have flown.